Study Of Barium Titanate-based And Bismuth Sodium Titanate-based Lead-free Electrcstrictive Ceramics Properties

Electrostrictive effect can achieve electromechanical conversion and has the advantage of low hysteresis strain.Thus,it can be applied in micro-displacement actuators.Previous studies have focused on lead-based relaxors for the electrostrictive effect,but with the development of green environment protection requirements,people gradually pay attention to lead-free system.Nominal formulas as(1-x)BaTiO3-xBi(Li0.5Nb0.5)O3(BT-xBLN)(x=0.02,0.04,0.08)and(1-X)(Na0.5Bi0.5)TiO3-xBa0.85Ca0.15Zr0.1Ti0.9Q3(NBT-xBCZT)(x=0.24,0.32,0.36,0.44)were designed and fabricated in this article.The XRD,SEM,dielectric and ferroelectric property were carried out in these two system,and the structure evolution,surface morphologies,dielectric,ferroelectric and electrostrictive properties were studied and the relationship of thermal stability consistency between the strain and polarization(relative dielectric constant)was discussed.(1)For BT-xBLN system,that the evolution from tetragonal P4mm symmetry to cubic Pm-3m symmetry was discovered in x=0.08 composition was studied by XRD refinement.The dielectric relaxation of component x=0.08 was observed at low temperature dielectric measurements,and a stable dielectric platform appeared in the temperature range of-55??125?.The dielectric thermal change rate of component x=0.08 was ??r/?25?±15%,which met the requirements of X7R capacitor standard.From 30? to 120?,the strain with low hysteresis and high thermal stability in composition x=0.08 was indicated by ferroelectric measurement.However,its strain level was only 0.024%.From the experimental data,that the thermal stability of strain originates from the thermal stability of dielectrics was proved by dielectric and ferroelectric measurement.The electrostrictive coefficient Q33 of BT-xBLN system was calculated to be 0.037?0.049 m4/c2.(2)For NBT-xBCZT system,that lattice constants and cell volumes increase accordingly,since the introduction of large radius ion Ba2+ and all compositions average crystal structure show pm-3m pseudocubic was indicated by XRD refinement That the NBT-xBCZT system exhibit obvious relaxation was showed by dielectric measurements and flat dielectric platforms was discovered in compositions x= 0.32 and x= 0.36.From 30? to 150?,polarization decreases around 20%in all studied compositions,and the maximum strain 0.112%achieved in composition x=0.36 under 50 kV/cm electric field.With the increase of temperature to 150?,the strain can still be maintained to 64%.It was proved that the thermal stability of strain is related to the thermal stability of polarization.The electrostrictive coefficient Q33 of NBT-xBCZT system was calculated to be 0.0282?0.0314 m4/c2.